Combating ferrous metal corrosion



United States PatentO COMBATING FERROUS METAL CORROSION Paul H. Cardwell and Charles L. Lunsford, Tulsa, Okla., assignors to The Dow Chemical Company, lvlidland, Micln, a corporation of Delaware No Drawing. Application June 4, 1952,

' Serial No. 291,787

8 Claims. (Cl. 252-855) The invention relates to corrosion inhibiting methods. It more particularly concerns an improved corrosion inhibiting composition for combating corrosion of ferrous metal parts of petroleum wells by corrosive agents accompanying the production of petroleum fluids.

- Corrosion by the produced fluids of the ferrous metal parts in deep wells in oil, gas, and condensate fields is a serious problem and oftentimes extends to the pipes and associated equipment attached to the wells above ground through which the produced fluids pass. The corrosive agents of petroliferous fluids are oftentimes acidic in nature, the acidic character being'due in many cases to such agents as hydrogen sulfide, carbon dioxide, organic acids, acid sulfur compounds, and inorganic salts carried in solution in water with the fluids entering the wells. Although a number of corrosion inhibiting agents have been proposed for injection into wells heretofore in attempts to combat the tendency for the produced petroliferous fluids to corrode the ferrous metal equipment of the wells, none has reduced the rate of corrosion of the ferrous metal'parts to the desired extent. Accordingly, it is a desideratum in the art to provide more effective inhibition of corrosion of the ferrous metal parts of deep i\filvellis which are subject to corrosion by the produced It is the principal object of the invention to provide an improved corrosion inhibiting composition for use in deep wells equipped with the usual ferrous metal parts, such as a casing and eductor equipment including the usual tubing stringso as to increase the effective life of these parts. Other objectsand advantages will appear as the description of the invention proceeds.

The invention is predicated upon the discovery that by mixing together dibutyl thiourea and an alkali metal alkyl sulfonamidoacetate having the formula of the well while on production these parts are effectively i protected from corrosion by the corrodants accompanying the petroleum fluids entering the Well. The invention then consists of the improved corrosion inhibiting composition and method of combating corrosion in deep wells herein fully described and particularly pointed out in the claims.

In carrying out the invention, the sulfonamidoacetate compound is mixed with the thiourea compound to form an inhibitor mixture and a suitable solvent vehicle therefor is added. We have found that the liquid coal-tarnitrogen bases may be used for the purpose of a solvent vehicle and they have the advantage of rendering the inhibitor mixture soluble in liquid hydrocarbons, such as gasoline, kerosene, fuel oil, and the like, thereby permitting the use of these liquids as additional diluents, if desired. Examples of suitable coal-tar-nitrogen bases are 2,4-lutidine, 2,6-lutidine, pyridine, quinoline, alpha-collidine, beta-collidine, gamma-collidine, alpha-picoline, beta-picoline, and gamma-picoline. The inhibitor mixture may be made into a solid form, such as in the form of sticks, if desired. This is accomplished by mixing the inhibitor mixture with molten paraflin wax. The resulting mixture is cast into sticks having a diameter permitting them to be dropped into a well through the tubing string. The resulting mixtures, either liquid or solid, are introduced into the well while on production. The liquid form of the mixture may be lubricated into the annulus. The

solid form may be dropped into the well through the tubing string.

The relative amounts of the inhibiting components of the inhibitor mixture may be varied over a Wide range, such as from 2 to 75 per cent by weight of the thiourea compound, 2 to 75 per cent of the sulfonamido compound and 15 to 96 per cent of the liquid vehicle of coaltar-nitrogen bases. Preferred proportions are 4 to 50 per cent of the thiourea compound, 4 to 50 per cent of the sulfonamido compound and 25 to per cent of the liquid vehicle of coal-tar-nitrogen bases. As a further diluent, as already indicated, a liquid hydrocarbon may be added in amount up to 70 to 80 per cent of the weight of the solution of the inhibiting component in the liquid vehicle of coal-tar-nitrogen bases. If a solid hydrocarbon is used as a vehicle as when employing the inhibiting composition in stick form, there may be used from 20 to 96 per cent of wax.

The following examples are illustrative of the invention:

EXAMPLE 1 34 pounds of dibutyl thiourea and 36 pounds (4.14 gallons) of the sodium tetradecyl sulfonamidoacetate are dissolved in 29 gallons of 2,4-lutidine, thereby producing 37 gallons of solubilized inhibitor mixture. The solubilized inhibitor mixture is diluted with 63 gallons of Stoddard solvent, thereby making gallons of diluted inhibitor mixture. In first treating a well, it is desirable to coat the ferrous metal parts subject to corrosion with an initial coating. This is done by mixing 10 to 15 gallons of the diluted inhibitor mixture with 1 barrel of kerosene and then circulating the resulting kerosene diluted inhibitor mixture down the well tubing and up the annulus. After this initial coating treatment, the diluted inhibitor mixture is lubricated into the well at the rate of 1 gallon per day through the annulus while the well produces.

EXAMPLE 2 92 pounds of dibutyl thiourea and 97 pounds of sodium tetradecyl sulfonamidoacetate are dissolved in 78 gallons of commercial collidine, thereby forming 100 gallons of the solubilized inhibitor mixture. The solubilized inhibitor mixture is diluted with kerosene in the ratio of 3 pints of the solubilized inhibitor mixture per gallon of the resulting diluted inhibitor mixture. The resulting diluted inhibitor mixture is lubricated down the annulus of the well as it produces.

EXAMPLE 3 82 pounds of a commercial paraflin wax, melting in the range of to 200 F., 9 pounds of dibutyl thiourea and 9 pounds of sodium tetradecyl sulfonamidoacetate are melted together to form a uniform mixture which is molded into sticks weighing about 1 pound each. Once a day four of the sticks are dropped down the tubing of a producing gas condensate well.

EXAMPLE 4 17 pounds of dibutyl thiourea and 2.07 gallons of so dium tetradecyl sulfonamidoacetate were dissolved in 14.5 gallons of liquid commercial coal-tar-nitrogen bases boiling in the lutidine range. The resulting mixture was diluted with 31.5 gallons of Stoddard solvent. Test coupons of strips of sand blasted mild steel x 1" x 2 /2" were set in the upper end of the tubing string of a gas condensate well in contact with the produced gaseous fluid. The corrosion rate thus ascertained was 15 mils per year. (A one mil per year corrosion rate means that a metal surface exposed to the corrodant loses weight corresponding to a loss of thickness of 0.001 inch per year.) The gas condensate well was then given an initial treatment to coat the tubing string with the inhibitor mixture by mixing 5 gallons of the foregoing diluted inhibitor mixture with 9 gallons of kerosene and introducing the kerosene diluted mixture into the well through the tubing. The well was allowed to produce. Thereafter each day for the duration of the test of this example, there was introduced into the annulus one gallon of the kerosene diluted inhibitor mixture while the well was continuously on production. The rate of corrosion by the produced fluid was ascertained by similar test coupons located in the well. In the first two weeks after the initial coating treatment, the corrosion rate had declined to an average of 9.79 mils. Two weeks later the corrosion rate measured over the next two weeks had declined to an average of 3.34 mils, as shown by a second set of similar test coupons. A third set of test coupons located in the well for two weeks beginning two weeks after the previous test showed that the corrosion rate had declined still further to an average of 0.095 mil. Two weeks later, a fourth set of test coupons located in the well for two weeks did not show any appreciable corrosion from the produced fluid.

It has also been found that other thiourea, e. g. diethyl thiourea, diphenyl thiourea, and di-o-tolyl thiourea, may be used in similar manner to dibutyl thiourea along with the alkali metal alkylsulfona'midoacetate to reduce the corrosive attack of the petroliferous fluids on the ferrous metal parts of the well. The effectiveness of the combination of the thiourea compound with the alkali metal alkylsulfonamidoacetate is also demonstrated in the following tests in which the effectiveness in reducing corrosion of the individual substances of the combination were compared with that of the inhibiting substances in combination. In these tests, a 2 per cent aqueous solution of propionic acid maintained at 175 F. was used as the corroding medium and the tests coupons consisted of fiat pieces of mild steel (ASTM 1018) 5 x 1" x 2%". These were immersed in 150 ml. of the corroding medium for 6 hours and the loss in weight determined. The results are set forth in the following table.

Table Inhibitor Composition, p. p. m. Concentration Weight Loss Test of Coupon No 1 in 1grams r Thiourea p. p. m. zggg p. p. m. 6 0. 218 0. 101 0. 080

4 diethyl- 50 do 50 0. 065 5 diphenyL. 100 0. 095 6 0 50 sodium tetra- 50 0.063

decyl. 7 di-o-tolyL- 100 0. 046 8 d0 50 sodium tetra- 50 0.030

decyl. 9 dibutyl 100 0.060 10. 0 50 sodium tetra- 50 0.020

decy

P. p. m.=parts of inhibitor composition per million parts of corrosion medium.

By referring to the table, it is manifest that the combination of the thiourea compound with the sulfonamidoacetate compound produces a greater corrosion inhibiting effect than either one of the individual compounds.

We claim:

1. The method of inhibiting corrosion of the ferrous metal parts of deep wells by fluid entering the well from the contiguous earth formations which comprises depositing in the well to contact the ferrous metal parts therein a corrosion inhibiting mixture comprising 2 to per cent by weight of an alkali metal alkylsulfonamidoacetate having the formula CnH2n+1SO2NHCI-I2COOM in which n is 12 to 18 inclusive, and M is an alkali metal, and from 2 to 80 per cent of a thiourea selected from the group consisting of diethyl thiourea, diphenyl thiourea, di-o-tolyl thiourea, dibutyl thiourea.

2. The method according to claim 1 in which the corrosion inhibiting mixture is dispersed in a petroleum hydrocarbon.

3. The method according to claim 1 in which the corrosion inhibiting mixture is admixed with a petroleum hydrocarbon and a coal-tar-nitrogen base selected from the group consisting of 2,4-lutidine, 2,6-lutidine, pyridine, quinoline, alpha-collidine, beta-collidine, gamma-collidine, alpha-picoline, beta-picoline, and gamma-picoline.

4. The method according to claim 1 in which the corro sion inhibiting mixture is solidified in a medium of parafi'ln wax melting in the range of to 200 F.

5. A corrosion inhibiting composition comprising a mixture containing from 2 to 80 per cent by weight of an alkali metal alkylsulfonamidoacetate having the formula CnH27r+l-SO2NHCH2COOM in which n is 12 to 18, inclusive, and M is alkali metal, and from 2 to 80 per cent of a thiourea selected from the group consisting of diethyl thiourea, diphenyl thiourea, di-otoIyl thiourea and dibutyl thiourea.

6. A corrosion inhibiting composition according to claim 5 in which the mixture is dispersed in a petroleum hydrocarbon.

7. A corrosion inhibiting composition according to claim 5 in which the mixture is dispersed in a coal-tarnitrogen base selected from the group consisting of 2,4-lutidine, 2,6-lutidine, pyridine, quinoline, alpha-collidine, beta-collidine, gamma-collidine, alpha-picoline, betapicoline, and gamma-picoline.

8. A corrosion inhibiting composition according to claim 5 in which the mixture is admixed with a petroleum hydrocarbon and a coal-tar-nitrogen base selected from the group consisting of 2,4-lutidine, 2,6-lutidine, pyridine, quinoline, alpha-collidine, beta-collidine, gamma-collidine, alpha-picoline, beta-picoline, and gamma-picoline.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,472,400 Bond June 7, 1949 2,493,462 Menaul Jan. 3, 1950 2,523,898 Carlson Sept. 26, 1950 2,583,399 Wachter et al. Jan. 22, 1952 2,599,385 Gross et al. June 3, 1952 2,602,760 Michel et al. July 8, 1952 2,602,779 Moyer et al. July 8, 1952 

1. THE METHOD OF INHIBITING CORROSION OF THE FERROUS METAL PARTS OF DEEP WELLS BY FLUID ENTERING THE WELL FROM THE CONTIGUOUS EARTH FORMATIONS WHICH COMPRISES DEPOSITING IN THE WELL TO CONTACT THE FERROUS METAL PARTS THEREIN A CORROSION INHIBITING MIXTURE COMPRISING 2 TO 80 PER CENT BY WEIGHT OF AN ALKALI METAL ALKYLSULFONAMIDOACETATE HAVING THE FORMULA CNH2N+1-SO2NHCH2COOM IN WHICH N IS 12 TO 18 INCLUSIVE, AND M IS AN ALKALI METAL, AND FROM 2 TO 80 PER CENT OF A THIOUREA SELECTED FROM THE GROUP CONSISTING OF DIETHYL THIOUREA, DIPHEYL THIOUREA, DI-O-TOLYL THIOUREA, DIBUTYL THIOUREA. 